The present invention relates to improvements to fluorination reactions using elemental fluorine in which HF is formed as a byproduct. In particular, the present invention relates to fluorination reactions in which the reactants are contacted in the presence of an HF-adsorbing composition, so any HF formed is removed from the reaction system to prevent the formation of other undesirable hydrogen-containing byproducts. The present invention also relates to improved fluorination reactors with reaction zones packed with HF-adsorbing compositions.